The present invention relates to tuning systems for television receivers and the like including memories for storing information corresponding to various tuning positions.
Recently, a number of memory type tuning systems for television receivers which include memory locations for storing binary signals representing information corresponding to various tuning positions have been proposed. In these systems, upon the selection of a particular tuning position, the binary signals stored in the memory are "read out" and converted to display information for visually indicating the selected tuning position and tuning information for controlling the frequency of the receiver's local oscillator to tune the receiver to the selected tuning position. These memory type tuning systems have various forms. Some of these systems, such as the General Instrument Corporation "Omega" system described in an article entitled, "Digital Television Tuner Uses MOS LSI and Nonvolatile Memory" by Lester Penner appearing in the Apr. 1, 1976 issue of Electronics, provide enough memory locations for storing information corresponding to all the tuning positions in a predetermined tuning range. For example, in the United States at least 82 memory locations would be provided for the 82 channels comprising the conventional VHF and UHF television bands. In other memory type tuning systems, such as the Magnavox Videomatic Touch Tune Assembly described in the Magnavox Manual 7353, published by the Magnavox Company, Fort Wayne, Indiana, for the sake of economy, there are provided only enough memory locations to store information corresponding to a limited number of preferred tuning positions. Still other memory type tuning systems of various kinds are disclosed in U.S. Pat. Nos. 3,778,736; 3,882,400; 3,940,702; 3,953,801; 3,968,440; 3,968,443; 3,979,680; 3,990,027; 3,999,131; 4,023,107; laid open Japanese Patent Application 50-16044; and an article entitled, "Working with Microprocessors -- Select the Station the Micro Way" appearing in the Apr. 13, 1977 issue of Electronics Weekly.
In those memory type tuning systems in which the memory contains enough memory locations to store information for a limited number of preferred tuning positions, it is necessary for a user to enter information for the preferred tuning positions into the memory because the preferred tuning positions differ depending on the user's location. Since this includes the entry of both display and tuning information, the entry procedure may be somewhat complex and may be the reason why this type of tuning system has not been fully accepted.
One possible difficulty that may be faced by a user is that he or she may not be aware of the condition of the memory. For example, if all of the limited number of memory locations contain information for corresponding tuning positions entry of information for an additional tuning position may cause previously stored information to be lost without the knowledge of the user. On the other hand, if none of the memory locations contains information corresponding to a tuning position, the receiver will not produce intelligible information for any selected channel and a user may be confused into thinking there is a major malfunction and, as a result, may initiate an unnecessary and costly service call.